Dose control for optical maskless lithography

Abstract

A lithographic apparatus comprises a patterning device, a projection system, and a controller. The patterning device is configured to pattern a beam of radiation. The radiation beam comprises a plurality of pulses of radiation. The projection system is configured to project the patterned beam of radiation onto a substrate coated with a layer of radiation sensitive material. The controller is arranged to control a total energy of a respective pulse of the plurality of pulses of the radiation beam. The controller is configured to take into account information indicative of properties of the layer of radiation sensitive material on a part of the substrate onto which the radiation beam is to be projected.

1 . A lithographic apparatus, comprising:
 a patterning device configured to pattern a beam of radiation, the radiation beam comprising a plurality of pulses of radiation;   a projection system configured to project the patterned beam of radiation onto a substrate coated with a layer of radiation sensitive material; and   a controller arranged to control a total energy of a respective pulse in one of the plurality of pulses of the radiation beam, the controller being configured to take into account information indicative a property of the layer of radiation sensitive material on a part of the substrate onto which the radiation beam is to be projected.   
   
   
       2 . The lithographic apparatus of  claim 1 , wherein the controller is configured to control the total energy of the respective pulse without changing a configuration of the patterning device. 
   
   
       3 . The lithographic apparatus of  claim 1 , wherein the controller is configured to take into account information indicative of the thickness of the layer of radiation sensitive material on the part of the substrate onto which the radiation beam is to be projected. 
   
   
       4 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to control the total energy of the respective pulse by controlling an intensity of the respective pulse. 
   
   
       5 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to control the total energy of the respective pulse by controlling a duration of the respective pulse. 
   
   
       6 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to control the total energy of the respective pulse by controlling a source of the radiation beam. 
   
   
       7 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to control the total energy of the respective pulse by controlling an apparatus in a beam path of the radiation beam. 
   
   
       8 . The lithographic apparatus of  claim 1 , wherein the patterning device comprises a plurality of arrays of individually controllable elements. 
   
   
       9 . The lithographic apparatus of  claim 8 , wherein the plurality of arrays of individually controllable elements are arranged in a row. 
   
   
       10 . The lithographic apparatus of  claim 8 , wherein the plurality of arrays of individually controllable elements are arranged in two rows. 
   
   
       11 . The lithographic apparatus of  claim 10 , wherein the two rows are parallel to one another and spaced apart from one another. 
   
   
       12 . The lithographic apparatus of  claim 11 , wherein the arrays of individually controllable elements of a first row are aligned with spaces in-between arrays of a second row. 
   
   
       13 . The lithographic apparatus of  claim 12 , wherein the arrays of individually controllable elements of the first row are positioned such that their footprints overlap with those of the arrays of individually controllable elements of the second row, such that the radiation beam may be projected onto different parts of the substrate. 
   
   
       14 . The lithographic apparatus of  claim 13 , wherein the controller is arranged to control the total energy of the plurality of pulses of the radiation beam, such that the difference in energy between respective ones of the plurality of pulses applied to the layer of radiation sensitive material beneath overlapping footprints is below about 0.1%, 0.5%, 1.0%, 2.0%, or 3.0%. 
   
   
       15 . The lithographic apparatus of  claim 1 , wherein the substrate is configured to move relative to the patterning device. 
   
   
       16 . The lithographic apparatus of  claim 1 , wherein the substrate is moveable relative to the patterning device. 
   
   
       17 . The lithographic apparatus of  claim 1 , wherein the patterning device comprises an array of individually controllable elements, which comprise mirror arrays. 
   
   
       18 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to receive information indicative of the properties of the layer of radiation sensitive material. 
   
   
       19 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to store information indicative of the properties of the layer of radiation sensitive material. 
   
   
       20 . The lithographic apparatus of  claim 1 , wherein the radiation sensitive material is photo resist. 
   
   
       21 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to control the total energy of the plurality of pulses of the radiation beam. 
   
   
       22 . The lithographic apparatus of  claim 1 , wherein the controller is arranged to individually control the total energy of each pulse of the plurality of pulses of the radiation beam. 
   
   
       23 . A lithographic method, comprising:
 patterning a beam of radiation, the radiation beam comprising a plurality of pulses of radiation, using a patterning device;   projecting the patterned beam of radiation onto a substrate including a radiation sensitive material thereon; and   controlling a total energy of a respective pulse in the plurality of pulses of the radiation beam taking into account information indicative of properties of the radiation sensitive material on a part of the substrate onto which the radiation beam is to be projected.   
   
   
       24 . The lithographic method of  claim 23 , wherein the total energy of the respective pulse is controlled without changing a configuration of the patterning device. 
   
   
       25 . The lithographic method of  claim 23 , wherein the information indicative of properties of the radiation sensitive material comprises information indicative of a thickness of the radiation sensitive material on the part of the substrate onto which the radiation beam is to be projected. 
   
   
       26 . The lithographic method of  claim 23 , wherein the information indicative of the properties of the radiation sensitive material on the part of the substrate onto which the radiation beam is to be projected is obtained from a reference substrate. 
   
   
       27 . The lithographic method of  claim 23 , wherein information indicative of properties of the radiation sensitive material across a surface of the substrate onto which the radiation beam is to be projected is obtained from a reference substrate. 
   
   
       28 . The lithographic method of  claim 23 , wherein the information indicative of the properties of the radiation sensitive material on the part of the substrate onto which the radiation beam is to be projected is obtained from determining a plurality of linear profiles of resist properties across a reference substrate. 
   
   
       29 . The lithographic method of  claim 26 , wherein the information indicative of the properties of the radiation sensitive material is obtained from the reference substrate before any radiation is projected onto the substrate onto which radiation is to be projected. 
   
   
       30 . The lithographic method of  claim 23 , wherein the information indicative of the properties of the radiation sensitive material on the part of the substrate onto which the radiation beam is to be projected is obtained from an analysis of critical dimension uniformity of a pattern or patterns applied to a reference substrate. 
   
   
       31 . A device manufacturing method, comprising:
 patterning a beam of radiation using a patterning device, the radiation beam comprising a plurality of pulses of radiation;   projecting the patterned beam of radiation onto a substrate including radiation sensitive material thereon; and   controlling a total energy of a pulse of the radiation beam taking into account information indicative of properties of the radiation sensitive material on a part of the substrate onto which the radiation beam is to be projected.